Back in the day (90s-ish is when it ramped up it seems), four frame materials were the most common in the industry, and each had a firmly defined list of pros and cons:
Steel Pros: Lively ride, durable, relatively inexpensive
Steel Cons: Heavy, flexy, rusts
Aluminum Pros: Light, stiff, doesn't rust, relatively inexpensive
Al Cons: Harsh ride, prone to cracking
Carbon Pros: Light, absorbs road vibration
Carbon Cons: Expensive, can feel "dead," prone to catastrophic failure
Titanium Pros: Light, lively (magic ride quality), durable, "forever frame" material
Ti Cons: Expensive, expensive, expensive
And back in the day, most of this was true. Big brands like Trek were still putting out high-quality steel frames that rode really well, aluminum frames really were stiff, especially in light of the primitive and uncommon suspension of the time, carbon was the new (to the mainstream) wonder material. Ti was always there, and it's always been seen as prohibitively expensive.
Fast forward a few decades, and advances in manufacturing and economies of scale, and with the exception of the cheapest frames, all of this is now utter and complete bullshit. The fact is, in the hands of a good brand or builder, any frame material can be made to perform any way the designer wants (and yes, how a frame "feels" is performance). A steel frame (Speedvagen) is the stiffest frame ever tested by VeloNews. The CAAD bikes from Cannondale and the Smartweld Allezs from Specialized are marvels of metal manipulation and ride insanely well, with no "harshness" to speak of. Carbon has gotten dramatically cheaper, and because it's been the trendy material for decades, there are a ton of garbage carbon frames out there that ride like shit. And ti is still there, and it's still expensive.
As is my common refrain, so the fuck what? Here's the problem with focusing on frame material: again, with the exception of really cheap (cheaply made and cheap to buy) frames, the frame material has less to do with the enjoyment of the ride than all these other factors (listed roughly in order of importance/impact):
- Your shorts and the quality of the chamois therein
- The fit of your bike
- Your gloves and bar tape
- The size of your tires and tire pressure thereof
- The quality of the drivetrain of the bike
- The quality of the wheels on your bike
As I explained elsewhere, a bike is a study in economics, and buying a bike with a more expensive carbon frame means you have less money for the above variables. That's not to say there aren't wonderful, inexpensive carbon bikes out there these days. There are, and more every season. It's just that when you walk into a shop, or hop on the interwebs, and say, "I want a carbon bike," it frames the issue in a way that makes it harder and more expensive to achieve the ultimate goal of getting a bike that you'll enjoy riding.
So bottom line, test ride a shit ton of bikes, and take them out for a real ride, where you go over a variety of surfaces, have to fight the wind and a couple hills, and need to shift a bunch. Then buy the nicest one you can afford. Then ride the shit out of it.